Researchers at the Max Planck Institute for Terrestrial
Microbiology, Marburg, Germany, have compared the microbial ecosystems in the
intestines termites and cockroaches, with fascinating results. The research is
published in the April Applied and
Environmental Microbiology.

It may be hard for people outside of certain scientific
domains to muster anything but disgust for termites and cockroaches.
Cockroaches, after all, infest our homes, and termites eat them. But despite
their different life strategies—termites feed exclusively on wood, while
cockroaches are the epitome of omnivory—these two culturally stigmatized
insects are closest relatives. The microbial denizens of the termite gut have
been the objects of intense study by microbiologists, with the goal of greatly
boosting the conversion efficiency of cellulosic materials to biofuels, but
cockroaches’ intestinal inhabitants have gone ignored, despite suspicions that
pathogens are among them.

“We wanted to determine to what extent, despite striking
differences in diet, the gut community of cockroaches resembles that of their
closest relatives, the termites,” says coauthor Claire L. Thompson. “We found
that termites and cockroaches contain many gut bacteria of the same families,
which indicates that the evolutionary history of the host is an important
factor determining the structure of the gut microbial community. However, we
found also that the abundance of these different lineages differs fundamentally
between termites and cockroaches, which we ascribe to their different diets.”
In fact, she says, the relative abundance of different bacterial groups in the
cockroach gut more closely resembles that of other omnivores, such as humans
and mice.

“Our research suggests that the gut microbiota of termites
and cockroaches reflects both their common evolutionary origin and their
different feeding habits,” says Thompson. “Many bacterial lineages seem to have
been associated with the cockroaches already when the termites split off more
than 130 million years ago.” Additionally, the researchers showed that the
bacterial community of the cockroach intestine is “much more complex than it
appeared from previous cultivation-based studies,” and disease causing
microorganisms therein “are actually quite rare.”

In the paper, the researchers note that termites fall within
the radiation of cockroaches, and that they “should be considered merely a
family of social cockroaches.” But current taxonomy has yet to catch up with
these relatively recent findings.

(C. Schauer, C.L. Thompson, and A. Brune, 2012. The
bacterial community in the gut of the cockroach Shelfordella lateralis reflects the close evolutionary relatedness
of cockroaches and termites. Appl. Environ. Microbiol. 78:2758-2767.)